This invention relates to a control mechanism for a bedroll of a rewinder. More particularly, the invention relates to a lockout cam for controlling the actuation of the transfer pins and the transfer pads of a bedroll.
Rewinders are used to convert large parent rolls of paper into retail sized rolls of bathroom tissue and paper towels. Two types of rewinders are commonly usedxe2x80x94center rewinders and surface rewinders. Center rewinders are described, for example, in U.S. Reissue Pat. No. 28,353 and wind the web on a core which is rotated by a mandrel. Surface rewinders are described, for example, in U.S. Pat. Nos. 4,723,724 and 5,104,055 and wind the web on a core which is rotated by a three roll cradle.
The critical operation in both center rewinders and surface rewinders is the sequence of steps referred to as cutoff and transfer. The web must be severed to end the winding of one roll, the leading edge of the severed web must be transferred to a new core, and the new core must be rotated to begin winding a new roll. These steps must be accomplished repeatedly and reliably while the web is moving at high speed. It is also desirable that each roll have exact sheet count and that the web is wound uniformly and substantially without wrinkles.
The term xe2x80x9cbedrollxe2x80x9d refers to the main winding roll of a rewinder, either a center rewinder or a surface rewinder.
As described in U.S. Reissue Pat. No. 28,353, a bedroll is commonly used in conjunction with a chopper roll to sever the web after a predetermined length has been wound into a log and to transfer the leading edge of the severed web to a new core in a continuous winding process. In center rewinders a latch mechanism is commonly used to retain the severing and transferring mechanism in an inoperative position until the proper length of web has been wound onto the log. A cam follower is controlled by an electric solenoid or pneumatic cylinder to unlatch the latch mechanism to release the severing and transferring mechanism. The severing and transferring mechanism is then controlled by one or more cams to perform the cutoff and transfer operations on the web. The latch is thereafter reset by the cam to retain the severing and transferring mechanism in the inoperative position.
A conventional latch mechanism and a severing and transferring mechanism for center rewinders is described in detail in U.S. Reissue Pat. No. 28,353. The severing and transfer mechanism includes transfer pins 56, cutoff blades 58 and 59, and transfer pads 55, all of which are movably mounted in the bedroll. When the severing and transfer mechanism is unlatched, the pins 56 hold the web against the rotating bedroll while the web is severed by a chopper roll 49 and the blades 58 and 59 (see FIGS. 20 and 21). The transfer pads thereafter urge the leading end of the severed web against a new core 53 (FIGS. 22 and 23).
The latch mechanism and the severing and transfer mechanism of U.S. Pat. No. Re. 28,353 are mounted on the bedroll and rotate with the bedroll. When the cam followers are latched during normal winding, the cam followers are spaced about 0.025 to 0.040 inch from the cams. When the solenoid is actuated to unlatch the latch mechanism, the impact between the cam followers and the cams can cause undesirable noise, vibration, and wear. The solenoid is also subject to wear and must be replaced periodically.
Surface rewinders sold by Paper Converting Machine Company of Green Bay, Wis. under the name xe2x80x9cMagnumxe2x80x9d include similar movable pins in a bedroll for holding the severed web against the bedroll and a similar latch mechanism for retaining the pins in an inoperative position until the web is to be severed. A cutoff knife is movably mounted in a chopper roll and is retained in an inoperative position by a latch mechanism which is similar to the latch mechanism which-is used on the bedroll of a center rewinder.
U.S. Pat. No. 6,179,241 describes a latch mechanism which is controlled by a camshaft which is mounted axially in the bedroll and by a servo motor which rotates the camshaft. The servo motor normally rotates the camshaft in the same direction and at the same speed as the bedroll. When the web is to be severed, the speed of the servo motor is either increased or decreased to rotate the camshaft relative to the bedroll. The rotation of the camshaft allows push rods in the bedroll to move radially inwardly to release the severing and transferring mechanism. Cam followers for the severing and transferring mechanism engage a stationary cam and control the movement of the mechanism. After the web is severed and transferred, the camshaft is rotated to force the push rods radially outwardly to relatch the severing and transferring mechanism.
The invention mounts the cam followers and cams outside of the bedroll. The cam followers and cams are easier to set up and replace and are less expensive than the traditional camming mechanism of U.S. Pat. No. Re. 28,353, and the need for a solenoid is eliminated. The cam followers ride on a lockout cam during normal winding. For cutoff and transfer, the lockout cam is rotated to allow the cam followers to engage pin and pad cams without excessive impact or vibration.
The independently rotatable lockout cam is driven by a servo motor at a speed which is matched to the bedroll during most of the winding cycle. During normal winding, a circular portion of the lockout cam is positioned under the pin and pad cam followers. As the bedroll approaches the point in the cycle where cutoff and transfer are to occur, the servo motor decelerates the lockout cam. During approximately the last three bedroll revolutions of the winding cycle, the lockout cam rotates relative to the bedroll to a point where a window in the lockout cam is aligned with the cam followers. The window allows the cam followers to engage and follow the contours of the pin and pad cams, thereby causing the required cutoff and transfer motions of the pins and pads.